ive heard all this before and it makes sense, but if all of this is true, then what is different about the BFR in 30-30 that allows it to work properly? just curious is all.

Havok7416

January 2, 2013, 11:12 PM

If I'm not mistaken .30-30 headspaces on the cartridge rim, thus alleviating that issue.

rcmodel

January 2, 2013, 11:19 PM

Look at the sharp shoulder angle of most bottleneck cases compared to the shallow shoulder angle of the 30-30 case.

The sharper the shoulder angle, the tighter it wedges against the recoil shield after the case expands.

The 7.62x39 also runs a little higher pressure then the 30-30. (42,000 vis 45,000 PSI.)

The 30-30 also headspaces on a rim, as opposed to the 7.62x39 headspacing on the shoulder.

So tolerances (slack between the case and recoil shield) are a little looser with the rimmed 30-30 case.
The rimless 7.62x39 has to start out already tighter then the rimmed 30-30 because it headspaces off the shoulder.

rc

JEB

January 2, 2013, 11:28 PM

ah-ha! thanks for that rc, i hadn't even thought about the rimmed/rim-less issue. thanks for clearing all that up for me!

R.W.Dale

January 2, 2013, 11:49 PM

As an owner of a 30-30 bfr all in all I found that setback issues were for the most part overblown.

IF

And this is a big if

I took the time to remove all traces of oil or lubrication from the cylinder bores prior to shooting with an alcohol soaked swabbing. Failure to do so would result in a bound up revolver.

Now would this be effective on a revolver chambered for the higher pressured more heavily tapered 7.62x39 I know not. That would be a $1500 question

posted via that mobile app with the sig lines everyone complains about

rcmodel

January 3, 2013, 12:03 AM

You don't see anybody successfully making them though do you?

For more insight, Goggle the S&W Model 53 .22 Remington Jet.

They tried their best, (1961 - 1971) and failed.

And if S&W couldn't do it then with Remingtons best brass case ammo?

Don't hold your breath for anyone else doing it with a 7.62x39 that has to work with old mil-sup steel case corrosive ammo.

On the other hand, maybe somebody with one of those 3-D printers is making one as we speak?
Rep. Steve Israel the (D-NY) congress critter has already called for a ban on them, just not in 7.62x9.

rc

BCRider

January 3, 2013, 02:10 PM

As someone that is strongly into metal working as a hobby and that has read about some of the physics of the metallurgy in the field this bit by RW about cleaning the casings and chambers is a key point. It shows just how important it is to increase the frictional coefficient between the two metals by ensuring there isn't ANY lubrication at all. Combine this with the rather slack shoulder angle of the .30-30 compared to other casings and it's pretty apparent why bottle neck cartridges simply don't work well in revolvers. And in those where it does, such as the .30-30 BFR, just how marginal it is that it works at all.

First off it really doesn't matter if the case is rimless or not or if it headspaces off a rim or shoulder. The brass is going to balloon under pressure and try to jam the case head against the recoil shield at the same time that the brass deforms the shoulder to fill the space. Keep in mind that under these sorts of pressures the brass is pretty much as strong as silly putty. It's the steel of the cylinder and recoil shield that keeps it all together. So other than a minimal amount of spring back the thin walls of the brass is going to be blown out to fill whatever void it can regardless of rimmed or not. And with a sharp shoulder angle that spells "locked up".

The one saving grace to a .30-30 is that the shoulder is at a longer taper angle. So even a minimimal amount of spring back means that the shoulder let the casing move ahead a trifle more than a steeper shoulder.

THen on top of this if the frictional coefficient can be increased by de-greasing the surfaces between the case and chamber you get just enough less movement and a trifle more spring back out of the sidewalls of the case. This all spells just enough play that RW's gun works when he does all these details to assist it.

So.... What is needed to make bottle neck cartridges work in a revolver? Seems to me that there are two ways.

First option is that the cylinder needs to be wedged back against the recoil shield so there's no play to allow it to jump forward from the pressure at the shoulder. That's going to take some mechanical trickery that works in connection with the cylinder timing. I suspect that the resulting revolver would look quite different from what we have now in order to make such a locking device work. And I don't even want to think about how it would make the trigger feel to have to wedge the cylinder back as part of the trigger pull.

The second option would be some way to divert part of the chamber pressure to push the cylinder back against the recoil shield. I'm thinking that if the front of the throats were recessed so there's a flat recess of around .03 inch depth and around .5 inch diameter and that if the back face of the forcing cone were increased in size that the pressure in that recess could be enough to force the cylinder back. Due to mass and timing it may not prevent the case expanding but perhaps it would halt the expansion before full lockup or be enough to compress the case shorter by some amount so that the cases are not locked solidly in place between the two parts like a door wedge.

This last idea would certainly be something to play with if I were working for an actual firearms maker. If it worked could you imagine the number of small bore varmint cartridges that could then be used in hunting revolvers?

Of course I'm great for thinking up new solutions that someone else thought about many years before me.... :D I suspect that someone tried this and found that it simply didn't work long before this posting.

Shadow 7D

January 3, 2013, 02:14 PM

what about the 30 carbine revolvers?

rcmodel

January 3, 2013, 02:16 PM

They are not a bottleneck case.

The slight taper doesn't interfere with cylinder rotation.

rc

R.W.Dale

January 3, 2013, 02:44 PM

They are not a bottleneck case.

The slight taper doesn't interfere with cylinder rotation.

rc

Actually it can.

They'll usually get a little draggy but will usually still rotate if lube is present in the cylinder bores. Same applies to a 9mm revolver but to a lesser degree.

Yeah I owned one of the 30 cal blackhawks too. Needless to say I've just gotten in the habit of not overly oiling a revolver cylinder

posted via that mobile app with the sig lines everyone complains about

CraigC

January 3, 2013, 03:13 PM

I'm no fan of Gary Reeder but he has several bottleneck wildcat revolver cartridges that seem to work well.

firesky101

January 3, 2013, 04:54 PM

a rimless revolver with spring loaded tabs (like the charters) could fix this. I would love to have a .223 double action like in fallout.

rcmodel

January 3, 2013, 04:57 PM

It would take some mighty powerful little spring tabs to withstand firing a 55,000 PSI rifle cartridge and hold it in place from stretching.

It won't work!

rc

bluetopper

January 3, 2013, 07:25 PM

All this can be accomplished by having a groove/channel behind each chamber yet still inside the rear of the cylinder with a steel plate that could be slid shut from the perimeter of the cylinder closing off the rear of each chamber. Each rear plate must have a center hole for the primer to be hit. The chambers would have to be recessed in the rear of the cylinder quite a bit for this to be feasible.
Loading and unloading wouldn't be quick at all, but it could be done.

R.W.Dale

January 3, 2013, 07:56 PM

A much simpler fix might work

You'd make the recoil shield taper away from the actual firing pin bushing wich would then need to be highly polished and slightly raised.

Then you'd use a moon clip to keep the cases from rattling annoyingly when they're not in the firing position.

This way only the case that was fired could possibly drag.

On an aside note my scandium Smith seems to be made this way. The firing pin bushing is raised and slightly dome shaped. It seems to work fine but makes primers flatten like crazy

posted via that mobile app with the sig lines everyone complains about

BCRider

January 3, 2013, 09:04 PM

Firesky and parasite. Sadly niether of those options would work. The rimless catches for the reason rc stated and in the case of that disc unless it was a screw on part of the cylinder it would just be a locked in spacer wedged by the casing as effectively as if it were not there. After all, given the pressures and surface areas involved we're talking about an impact blow that is about on par with a healthy swing from a fairly big hammer. Half assed little .22short blanks push impresively sized nails into concrete and steel. And they are nothing compared to the pressure and area in a .30-30 or 5.56 round.

RW, I'd suggest that if the little raised area was present that it would merely punch an imprint into the back of the primer and part of the case head and lock things in place all the more firmly. If bottle neck revolvers are going to stand a chance then something more radical that prevents the stretch between the case head and shoulder is needed.

Jaymo

January 3, 2013, 11:41 PM

I'm thinking a .303 Brit revolver would make me giddy as a schoolgirl.
I could even load it with BP for fun.

blaisenguns

January 4, 2013, 02:15 PM

Dude if you want a "pistol" that fires that round, buy a Draco. Not really a good one hander, but it is pretty darn cool :D

rcmodel

January 4, 2013, 03:46 PM

You know, it just occured to me that Dillon Aero does make a 7.62x51 NATO revolver that works!

http://www.dillonaero.com/content/p/8/catid/1/pid/1/Standard_M134D

rc

blaisenguns

January 4, 2013, 05:46 PM

You know, it just occured to me that Dillon Aero does make a 7.62x51 NATO revolver that works!]

Hey thats not a revolver!!

Jim Watson

January 4, 2013, 05:57 PM

Experiment for the well heeled DIY:

Make a new barrel and cylinder for a S&W 547 in whatever bottleneck round will fit. Or just put a stock Jet barrel and cylinder in a 547 frame.
The 547 has a pin above the firing pin meant to hit the 9mm case head and drive it all the way into the chamber. Would the main and rebound spring be enough to keep a Jet from setting back? Only one way to find out.

If you enjoyed reading about "7.62x39 revolver" here in TheHighRoad.org archive, you'll LOVE our community. Come join TheHighRoad.org today for the full version!